8 Oct 2018 - Some Space missions run for years, or even decades. They need reliable power to run scientific instruments and communications equipment. Nuclear batteries, so-called Radioisotope Power Systems, provide energy for a very long time. Radioisotope Power Systems are thermoelectric devices. Other than reactors, which run on nuclear fission, they use the decay of radioactive material to produce heat and electricity. These nuclear batteries can run for 40 years without being charged.